<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
/*文档流中，子元素为块元素时宽度默认占父元素全部*/		
			.aaa{height:100px;
			     background-color:#bfa}

/*块元素脱离文档流后，宽高会被内容撑开（可自行设置）*/			     
			.bbb{height:100px;
				background-color:red;
			     float:left} 
			     
/*内联元素脱离文档流后会变成块元素*/			
			.ccc{width:100px;height:100px;
			     background-color:yellow;
			     float:left;}         
		</style>
	</head>
	<body>
		<div class="aaa"></div>
		<div class="bbb">bbb块元素</div>
		<span class="ccc">span</span>
	</body>
</html>
